function [ centers ] = get_3_tangent_circles_centers( r )
%The function gets a radius, and returns the centers of 3 tangent
%circles around (0,0)
centers = zeros(3,2);
centers(1,:) = [ -r, r/sqrt(3)];
centers(2,:) = [r, r/sqrt(3)];
centers(3,:) = [0, -2*r/sqrt(3)];
